7.4 PG_CLOG problems

Hi,


    Does anybody know what this means ?  "LOG:  removing file
"/var/lib/pgsql/data/pg_clog/0000",

    There were whole bunch of files got removed  from the  pg_clog
directory.      I saw this on my postgres 7.4 log while doing a vacuum
on a database last night, this database was never vacuumed before for
past one year.  The reason we didnt do any vacuum's before on this
because it was used only for SELECTS.

     Is this a problem something to worry about ?  my database seems to
working fine , I could run all my queries and everything seems to be fine.


Thanks!
Pallav.